This invention generally relates to a cooling system for a gas turbine engine, and specifically to a cooling system including a fuel deoxygenator to increase the usable heat absorption capability of fuel used for cooling cooling air.
A gas turbine engine typically includes a compressor, a combustor and a turbine. Air entering the compressor is compressed and directed toward the combustor. In the combustor, fuel is combined with the high-pressure air and ignited. Combustion gases produced in the combustor drive the turbine. High engine temperatures provide better fuel burn rates and engine efficiencies that extend the range of an aircraft. The high engine and combustion gas temperatures are greater than can normally be accommodated by metal parts of the engine. Typically, a portion of air from the compressor is bled off and directed over parts of the engine to form a cooling boundary layer that insulates exposed surfaces from the hot combustion gases.
Cooling the bleed air from the compressor allows the engine to be operated at increased combustion gas temperatures while maintaining the same temperature in engine components. It is known, to use fuel as a cooling medium to cool air from the compressor. The usable cooling capacity of fuel is limited by coke formation caused by oxidative reactions with dissolved oxygen within the fuel. These reactions cause the formation of insoluble materials referred to as “coke” or “coking”. Coke deposits can cause degradation of fuel delivery performance. Therefore, the usable cooling capacity of the fuel is limited by the amount of dissolved oxygen within the fuel. Further, the usable cooling capacity of the fuel limits the amount of heat that can be transferred from the engine cooling air, and that in turn limits sustainable engine operating temperatures.
Accordingly, it is desirable to develop an engine cooling system with increased fuel cooling capacity for absorbing greater amounts of heat from cooling air.